The SMF said it had tracked workingage households rather than relying on statistical averages and other data to make the findings.

The study said that in 2011–12 the average household in the middle of the income distribution scale had a realterm income 13 per cent lower than in 2007 because wages rose more slowly than inflation.

However, the SMF still found that 31 per cent of families had risen up one income group, while some 10 per cent had even jumped from the middle group to the top bracket of earners.

Ed Miliband, the Labour leader, has said that the middle class faces a "crisis of confidence" over living standards and their children's prospects that must be urgently addressed.

"The cost-of-living crisis is not just about people on tax credits, zero hours contracts and the minimum wage. It is about millions of middle-class families who never dreamt that life would be such a struggle," Mr Miliband said.

George Osborne, the Chancellor, has also been urged by many Conservative MPs to ease the tax burden on middleclass professionals. Senior Tories believe middle-class families need more help and had called on Mr Osborne to use his Budget to raise the 40p tax threshold.

Emran Mian, the director of the SMF, said: "In reality, the middle has coped surprisingly well since 2007-08. We found that even in the teeth of the recession, two fifths of them moved up the income distribution.

"With the recovery under way, their prospects are likely to improve further."